Catalytic-chemical vapor deposition (CAT-CVD) is a film formation method of supplying a reactive gas (source gas) to a catalyst wire heated to, for example, 1,500 to 2,000° C. and depositing decomposition species (deposited species) generated using catalysis or thermal decomposition reaction of the reactive gas on a base material to be film-formed.
The catalytic-chemical vapor deposition is similar to plasma CVD in that decomposition species of a reactive gas are deposited on a base material to thereby perform film formation. However, in the catalytic-chemical vapor deposition, decomposition species are generated using catalysis or thermal decomposition reaction of the reactive gas on a catalyst wire having a high temperature. Therefore, the catalytic-chemical vapor deposition has an advantage that surface damage due to plasma is not caused and a use efficiency of a source gas is high, as compared to the plasma CVD in which plasma is formed to generate decomposition species of a reactive gas.
For example, the catalytic-chemical vapor deposition is used when a silicon (Si)-based film is formed. Conventionally, for a catalyst wire used in the catalytic-chemical vapor deposition, a tungsten (W) wire is widely used (see, for example, Patent Document 1). However, tungsten is prone to undergo an alloying reaction with silicon (silicidation). When tungsten is silicided, cracks are generated on the surface and the mechanical strength is reduced, which shortens the service life of the catalyst wire.
On the other hand, examples of a material having a lower silicidation speed than that of tungsten include tantalum (Ta). There is a method of using a tantalum wire as a catalyst wire to form a silicon film (see, for example, Patent Document 2).
Patent Document 1: Japanese Patent Application Laid-open No. 2003-303780
Patent Document 2: Japanese Patent Application Laid-open No. 2003-247062.